Fungi Flashcards
Geographic location of Histoplasma capsulatum?
What is it found in and how is it transmitted?
- Midwestern and central US; along the Mississippi and Ohio River Valley
- Associated with bird or bat droppings. People in caves or cleaning chicken coops
- Transmitted through inhalation of spores into respiratory tract and then ingested by macrophages
What is the histological characteristic of macrophages that have picked up Histoplasma capsulatum?
Macrophages with intracellular oval bodies (ovoid bodies)
How does the structure of Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis change based on temperature?
- Dimorphic
- At 25 °C they grow as mycelia (mold)
- Inside body at 37 °C they are a yeast
*Coccidioidesformsspherules filled with endospores inside lungs
“Mold in the cold, yeast in the heat”
How is the diagnosis of Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioiodes immitis made?
1) Best diagnosed with biopsy of affected tissue - examined with silver stain or KOH prep
2) Serologic testing: rapid serum antigen test
3) Urine rapid antigen test (quickest)
What is the disease mechanism for Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioiodes immitis?
- Once inhaled, cause local infection in the lung
- Followed by bloodstream dissemination
What are the 3 clinical presentations for Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioiodes immitis?
1) Asymptomatic: majority of cases or mild respiratory illness
2) Pneumonia: mild w/ fever, cough, and chest X-ray infiltrates. Like Tb, granulomas with calcifications can follow resolution.
- Minority will develop chronic pneumonia and even less will progress to a chronic cavitary pneumonia
3) Disseminated, rarely can cause meningitis, bone lytic granulomas (osteomyelitis), skin granulomas (erythema nodosum), and organ leisions –> Most often in immunocompromised
Geographic location of Blastomycosis dermatitidis?
Transmitted how?
- Great lakes and Ohio River Valley
- Inhalation of aerosolized spores
What is the most prominent morophological characteristic of Malassezia furfur?
- “Spaghetti and meatball” appearane on KOH prep of skin scrapings
- Spaghetti = hyphae
- Meatballs = spherical yeast
Infection by Malassezia furfur causes what condition?
Manifests how?
- Pityriasis versicolor (tinea versicolor)
- Superficial fungal infection causing hypo- and/or hyerpigmented patches of skin on back and chest
- Confined to the STRATUM CORNEUM
Geographic location of C**occidioides immitis?
Route of transmission?
Second most common opportunisitc infection in whom?
- Found in the Southwestern U.S. (AZ, NM, SoCal)
- Inhalation of aerolized spores in dust
- 2nd most common opportunistic infection in AIDS patients who have resided in Arizona!
Exophiala werneckii is responsible for what superficial fungal infection?
Manifests how?
- Tinea nigra
- Dark brown to black painless patches on the soles of the hands and feet
Where is Sporothrix schneckii found?
Causes what condition?
- Soil and on plants (rose thorns and splinters)
- Rose gardener’s disease
Following a prick by a thorn contaminated with Sporothrix schneckii what occurs?
- Nodule at site of trauma becomes necrotic and ulcerates
- Infections spreads in ascending pattern along the path of draining lymphatic’s
Microsporum, Trichophyton, and Epidermophyton are the common?
Dermatophytes
What are 3 common sources of dermatophytes?
- Soil
- Animals
- Humans
In normal hosts (immunocompetent) infection by Candida albicans causes?
What specifically in infants?
1) Oral thrush: patches of creamy white exudate w/ a reddish base
2) Vaginitis: frequently when taking antibiotics, OCs, or during menses
3) Diaper rash: due to heat/humidity within diaper
In immunocompromised patients what does Candida albicans lead to?
Important implication in IV drug users?
- Candidal esophagitis often seen in HIV or diabetic patients
- Dissemination: NOT normally found in blood, but can invade almost any organ if it enters
- Renal, myocardial, and brain abscesses
- Can invade eye and cause endopthalmitis
- ENDOCARDITIS often tricuspid in IV drug users
How is the diagnosis of Dermatophytosis made?
What specific method for Microsporum species?
- KOH prep of skin scrapings: branched hyphae
- Woods light to diagnose Microsporum will fluoresce under UV light
Aspergillus fumigatus causes what 3 major types of disease?
What are the important characteristics of each?
1) Allergic bronchopulmonary pergillosis (ABPA) - type I hypersensitivity - wheezing, fever, migratory pulmonary infiltrate - IgE mediated
2) Aspergillomas - infection in preformed lung cavities (from TB or malignancies) - fungal ball
3) Angioinvasive aspergillosis - affecting immunocompromised (pt’s with neutropenia following chemo or on high dose steroids for tx of GVHD)
Microscopic examination of Sporothrix schneckii reveals?
Cigar shaped yeast cells that reproduce by budding
What is the morphology of Candida albicans based on temperature?
Pseudo hyphae at 25 °C and germ tubes at 37 °C
How is diagnosis of Candida albicans made?
- KOH stain of specimen
- Silver stain of specimen
- Blood culture: growth must be respected (not normally in blood)
- Blood assay for beta-D-glucan
Where in nature is Cryptococcus neoformans found?
How is it transmitted?
- Found in soil, but most often pigeon droppings
- Via inhalation and settles in lung as primary focus before disseminating
Phialophora and Cladosporium cause what fungal disease?
How does it manifest?
- Chromoblastomycosis
- Following puncture wound, a small, violet, wart-like lesion
- Over months-years, additional warts arise and eventually clusters of lesions resemble cauliflower
Skin scrapings with KOH of Chromoblastomycosis reveal?
Copper-colored sclerotic bodies
Rhizopus, Rhizomucor, and Mucor (Mucormycotina) are fungi responsbile for which opportunistic disease?
Murcormycosis
Aspergillus produces what toxin and what type of cancer is it associated with?
Often found contaminating what foods, which are common sources?
- Aflatoxin —> hepatocellular carcinoma
- Peanuts, grain, and rice
What is the morphology of Aspergillus fumigatus?
Acute angle branching WITH septations
*First 2 letters ‘AS’ –> Acute Septate
How is diagnosis of allergic bronchopulmonary asperigillosis made?
- High level of IgE and IgG against aspergillis
- Sputum culture
- Wheezing patient and chest X-ray with fleeting infiltrate
Who is most at risk for infection by Pneumocystis carinii (P. jiroveci)?
What does it cause?
Most common opportunistic infection in whom?
- Immunocompromised (AIDS, cancer, organ transplant recipients)
- Severe interstitial pneumonia called Pneumocystis carinii pneumonia (PCP)
*Most common opportunistic infection in AIDS patients
Which organs and tissues are most often affected by Angioinvasive aspergillosis?
- Primary lesions in lung –> necrotizing pneumonia
- Heart valves –> endocarditis
- Kidney —> renal failure
- Brain –> ring enhancing lesions
- Paranasal sinuses may causes necrosis around nose
What are the major morphological characteristics of Cryptococcus neoformans?
Only found in what form?
- Heavily encapsulated w/ repeating polysaccharides
- Only found in yeast form
What is the major manifestation of Cryptococcus neoformans infection?
How else can it manifest?
Who is most at risk?
- Subacute or chronic meningitis: headache, fever, vomiting, neuro deficits –> Most common cause of fungal meningitis (meningoencephalitis)
- Pneumonia: usually self-limited
- Skin lesions: which resemble acne
*Most often affects immunocompromised pt’s w/ AIDS, leukemi, lymphoma, SLE, or transplant recipients
What is the key to diagnosis of Cryptococcus neoformans?
What do you expect to see?
- A lumbar puncture then stain with India ink
- Yeast cells with a surrounding halo, the polysaccharide capsule
What stain for tissue samples of Cryptococcus neoformans?
What is another test that relies on the structure of this yeast?
- Stain with mucicarmine (red) or methanamine (silver)
- Can do latex agglutination test to detect repeating polysaccharide capsular antigen w/ antibody-coated beads causing agglutination
Who is most at risk for infection by Mucormycosis?
- Diabetics who develop profound DKA
- Immunocompromised patints, burn patients, and those taking iron chelator deferoxamine, whom are at risk for acidosis
What is the morphology of Mucomycetes (Mucormycotina)?
Hyphae are NON-septate rods w/ wide/right angle branching (90°)
What are the clinical features of Mucormycosis?
- Fungi proliferate in vessel wall where there is extra glucose and ketones
- After BV invasion, penetration of cribiform plate and invasion of brain
- Necrosis of tissus –> Rhinocerebral mucormycosis
- Can also cause pulmonary mucormycosis
What is the relationship between CD4 count and development of PCP?
When CD4+ count is below 200 there is increased risk of infection
Clinical features of PCP?
What is seen on X-ray?
- Present with: fever, SOB, and nonproductive cough
- Diffuse bilateral interstitial infiltrates, “ground glass” appearance
How is diagnosis of infection with Pneumocystis carinii (jiroveci) made; what characteristic shape are you looking for?
What is done to confirm diagnosis?
- Silver stain of alveolar lung secretions, revealing the saucer-appearing fungi
- Bronchoalveolar lavage or Biopsy by bronchoscopy to confirm the diagnosis
